CN112345698B - A grid layout method for air pollutant monitoring sites - Google Patents

Abstract

The present invention provides a grid arrangement method of air pollutant monitoring stations. The method includes three steps: the first step is coarse grid layout. According to the investigation of the local population and industry distribution, the frequency of pollution and the scope of pollution, the hotspot area is densified on the basis of uniform grid. The second step is to improve the grid adaptation degree of the hotspot area. According to the local meteorological conditions, the actual effective monitoring range of the monitoring station is obtained inversely based on the adjoint probability method, which provides data reference for the size of the fine grid; In the grid optimization step, according to the obtained effective monitoring range of the monitoring station, the optimal analysis technology is used to solve the grid distribution density and grid aspect ratio to achieve full coverage of the monitoring area. The invention can efficiently and accurately propose the layout scheme of monitoring grids according to the actual situation, has guiding significance for the location selection of monitoring sites and the evaluation of monitoring effects of existing sites, and is helpful for urban air management and improvement.

Description

A grid layout method for air pollutant monitoring sites

technical field

The invention belongs to the technical field of atmospheric environment monitoring and risk early warning, and in particular relates to a grid arrangement method of air pollutant monitoring sites.

Background technique

Air pollution has become a serious problem faced by modern cities. Unreasonable discharge of pollutants not only affects the environment, but also threatens the health of residents. The atmospheric environment monitoring network composed of air pollution monitoring stations, as the most direct means of atmospheric environment monitoring, can obtain real environmental pollution data, reveal the distribution of air pollutants in time and space, and its existence is important for the control and management of urban air pollution sources. And improving urban air quality is of great significance. The grid layout scheme of pollutant monitoring sites is a very important technical indicator, which is related to whether the potential pollution sources in the study area can be fully covered, and directly affects the effectiveness of monitoring site settings. If the grid-based monitoring points cannot be effectively distributed, it will bring great uncertainty to the monitoring and control of air pollution.

At present, the general atmospheric environment monitoring network adopts the method of uniform layout. This method is only reasonable when the pollution level of the monitoring area is relatively consistent, so the application conditions of this method are very limited. If the distribution of pollution sources, geographic information, meteorological characteristics and other factors are not considered, the plan of evenly distributing monitoring sites will be adopted, which will make data redundant in areas with low pollution levels, and insufficient monitoring data in areas with high pollution levels, thus affecting the monitoring level and wasteful. Human and material resources. Therefore, how to effectively establish a grid layout scheme of air pollution monitoring sites is a problem that must be considered by environmental monitoring departments.

Similar inventions, such as a satellite remote sensing-based atmospheric environment ground monitoring site deployment and networking method invented by Zhu Zhongmin (application publication number CN109655583A), this invention is based on satellite remote sensing technology, and obtains pollution geographic distribution and pollution evolution trend from historical satellite image information. and other information, and then deploy and control the network on this basis. The disadvantage of this invention is that it is completely based on historical pollution information, and is not applicable to areas lacking historical pollution data or types of pollutants that cannot be monitored by satellites.

Similar inventions such as a method for optimizing the layout of monitoring points for emergency monitoring of sudden air pollution accidents invented by Chen Tian (application publication number CN110084418A), the invention simulates the diffusion range and concentration distribution of pollutants after the accident based on a pollutant pollutant diffusion model. Gridding the range of the points according to the distribution characteristics of the environmental sensitive points. The disadvantage of this invention is that the simulation of pollutant diffusion is carried out on the basis of known release intensity and location of the pollution source, and the arrangement of monitoring points is after the accident occurs. If the monitoring points for the purpose of pollution prevention and early warning are to be deployed in areas with unknown pollution sources, this method is invalid.

Therefore, in view of the above problems, the present invention proposes a grid arrangement method for air pollutant monitoring sites. This method can propose a reasonable grid density distribution scheme based on geographical factors, and quantitatively describe the grid distribution density and grid aspect ratio by optimizing the calculation method according to the actual effective monitoring range of the monitoring station in the hotspot area, so as to realize the monitoring area. Full coverage. According to the actual situation, the invention efficiently and accurately proposes the layout scheme of the monitoring grid, which has guiding significance for the location selection of the monitoring site and the evaluation of the monitoring effect of the existing site, and is helpful for the management and improvement of urban air.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to guide the grid distribution scheme of urban air pollutant monitoring stations and to evaluate the monitoring effect of existing grid monitoring stations, and to solve the problem of difficulty in obtaining pollution information described in the patent (application publication number CN110084418A). The problem and the problem of time lag in the deployment and control of measuring points described in the patent (application publication number CN109655583A). A grid layout method for monitoring stations that can quantitatively describe the grid point density and grid aspect ratio to achieve full coverage of the monitoring area is proposed.

A grid arrangement method for air pollutant monitoring sites, comprising the following steps:

Step 1: Lay out the coarse grid.

For monitoring large areas, firstly, a uniform grid with an aspect ratio of 1:1 is used. Then, according to the investigation of the local population and industry distribution, the frequency of pollution, and the historical data of the pollution impact range, the densely populated and industrial enterprises are clustered. . Refine grids in hotspot areas with frequent historical pollution phenomena, and determine the grid refinement ratio through grid independence test;

The second step is to improve the fitness of the grid in the hotspot area.

According to the local prevailing meteorological conditions, the following methods are used to obtain the actual effective monitoring range of a single monitoring station, which provides data reference for the size of the fine grid.

Obtain the local wind speed and wind direction parameters as the velocity inlet boundary conditions, use computational fluid dynamics to solve the Navier Stokes equation, and calculate the flow field in the study area; C) Substitute into the adjoint equation of the pollutant propagation equation:

为探测区域位置矢量，

为测点位置矢量，C表示污染物浓度，u_j为x_j轴方向上的速度,v_c，j表示污染物C在x_j方向上的湍流扩散系数，q₀为污染物负源的单位体积流量，Γ₁,、Γ₂和Γ₃为边界条件，n_i为x_i轴方向的单位矢量。

为负荷项，其表达式如下：where ψ* is the accompanying probability factor of the position,

is the detection area position vector,

is the position vector of the measuring point, C represents the pollutant concentration, u _j is the velocity in the direction of the x _j axis, vc _{, j} represents the turbulent diffusion coefficient of the pollutant C in the direction of x _j , and q ₀ is the unit of the negative source of the pollutant Volume flow, Γ ₁ , Γ ₂ and Γ ₃ are boundary conditions, and _{ni is the unit vector in the direction of the x i axis} .

is the load term, and its expression is as follows:

将其代入求解如下概率方程(1-3)，得到不同污染源释放强度对应的潜在污染源位置的伴随概率分布，概率最大的位置就是污染物源最可能存在的位置，概率最大的位置围成的范围即为监测站在该源强条件下的监测范围：Solving the equation yields an adjoint probability distribution for the location of potential pollution sources

Substitute it into and solve the following probability equation (1-3), and obtain the accompanying probability distribution of the potential pollution source locations corresponding to the release intensity of different pollution sources. That is, the monitoring range of the monitoring station under the condition of the source strength:

和

分别为对应于监测站的位置P和监测浓度阈值C，M为污染源释放强度，

为根据监测阈值求得的相应污染物释放浓度M和位置x的概率分布。

的分布形式为正态分布：in

and

are the position P corresponding to the monitoring station and the monitoring concentration threshold C, respectively, M is the emission intensity of the pollution source,

is the probability distribution of the corresponding pollutant release concentration M and location x obtained according to the monitoring threshold.

The distribution is in the form of a normal distribution:

Among them, σ _ε is the measurement error of the instrument, which can be set to 20%. When applying this method to real cases, researchers can adjust the coefficient based on the actual error of the instrument.

Step 3: Optimization stage for the mesh.

According to the effective monitoring range of a single monitoring station in the site obtained in the second stage, the optimal grid point density and aspect ratio are obtained by using the optimization analysis technology, and the minimum number of monitoring points is used to achieve full coverage of the monitoring area.

Compared with the prior art, the beneficial effects of the present invention are:

In the calculation, the present invention only needs to obtain the meteorological parameters and the concentration monitoring threshold of the instrument, so as to predict the pollution monitoring range of different concentration ranges, and based on this, the grid control is carried out, and the data demand is small; according to the meteorological characteristics of the monitoring area , in the simulation calculation, the actual flow field and pollutant transfer situation are more restored, which can be efficient and accurate.

Description of drawings

FIG. 1 is a schematic flow chart of formulating a grid distribution scheme for urban air pollutant monitoring stations provided by the present invention.

FIG. 2 is a schematic diagram of arrangement of coarse grids and encryption of hotspot areas according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of an effective monitoring range of a pollutant monitoring station in different seasons provided by an embodiment of the present invention.

FIG. 4 is a schematic diagram of a grid distribution scheme for achieving full coverage of a monitoring area in different seasons according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of a coverage effect of original uniform grids in different seasons provided by an embodiment of the present invention.

Detailed ways

The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

Referring to Figure 1, it is a schematic diagram of the development process for the grid distribution scheme of urban air pollutant monitoring stations. This method consists of three stages: the first stage properly densifies hotspot areas on the basis of uniform grids based on the investigation of the distribution of local population and industry, the frequency of pollution and the scope of pollution; the second stage is based on the Based on the local meteorological conditions, the actual effective monitoring range of the monitoring station is reversely obtained based on the adjoint probability method, which provides a data reference for the size of the fine grid; in the third stage, based on the effective monitoring range of the monitoring station, the optimal analysis technology is used to solve the grid distribution density. And the aspect ratio of the grid to achieve full coverage of the monitoring area.

Taking a certain place as an example, the grid distribution of monitoring sites is divided into the following three stages:

The first stage is coarse grid layout. Refer to Figure 2. Before grid adjustment, the area to be tested adopts a uniform grid with an aspect ratio of 1:1. According to the distribution of the local population (Figure 2-1) and the severity of the pollution phenomenon (Figure 2-2) According to the investigation of historical data such as the influence range of pollution under dominant wind conditions (Figure 2-3), the grid should be properly densified for hotspot areas such as densely populated and severely polluted areas.

The second stage is to improve the degree of grid adaptation in hotspot areas. The following method is used to obtain the actual effective monitoring range of a single monitoring station, which provides data reference for the size of the fine grid.

According to the calculation requirements, it is necessary to compare the grid layout schemes of winter and summer. It is learned from the weather station that the dominant wind direction in summer is southerly, and the dominant wind speed is 1.3m/s; in winter, the dominant wind direction is northerly, and the dominant wind speed is 3.8m/s. Use computational fluid dynamics to solve the Navier Stokes equation to calculate the flow field in the study area; substitute the coordinates of a hot spot and the monitoring threshold (P, 75μg/m ³ ) of the instrument for pollutants into the adjoint equation of the pollutant propagation equation :

为探测区域位置矢量，

为测点位置矢量，C表示污染物浓度，u_j为x_j轴方向上的速度,ν_c，j表示污染物C在x_j方向上的湍流扩散系数，q₀为污染物负源的单位体积流量，Γ₁,、Γ₂和Γ₃为边界条件，n_i为x_i轴方向的单位矢量。

为负荷项，其表达式如下：where ψ* is the accompanying probability factor of the position,

is the detection area position vector,

is the position vector of the measuring point, C represents the pollutant concentration, u _j is the velocity in the direction of the x _j axis, ν _{c, j} represents the turbulent diffusion coefficient of the pollutant C in the x _j direction, and q ₀ is the unit of the negative source of the pollutant Volume flow, Γ ₁ , Γ ₂ and Γ ₃ are boundary conditions, and _{ni is the unit vector in the direction of the x i axis} .

is the load term, and its expression is as follows:

将其代入求解如下概率方程(1-3)：Solving the equation yields an adjoint probability distribution for the location of potential pollution sources

Substitute it to solve the following probability equation (1-3):

和

分别为对应于监测站的位置P和监测浓度阈值C，M为污染源释放强度，

为根据监测阈值求得的相应污染物释放浓度M和位置x的概率分布。一般将

的分布形式定义为正态分布。其中σ_ε为仪器的测量误差，设为20％。：in

and

are the position P corresponding to the monitoring station and the monitoring concentration threshold C, respectively, M is the emission intensity of the pollution source,

is the probability distribution of the corresponding pollutant release concentration M and location x obtained according to the monitoring threshold. will generally

The distribution form of is defined as a normal distribution. Among them, σ _ε is the measurement error of the instrument, which is set to 20%. :

Solve equation (1-3) to obtain the accompanying probability distribution of the corresponding potential pollution source location when the release intensity is greater than 40g/s. The location with the highest probability is the location where the pollutant source is most likely to exist, and the range enclosed by the location with the highest probability is The monitoring range of the monitoring station under the condition of the source strength (see Figure 3, the effective monitoring range in calm wind conditions, summer and winter, respectively)

The third stage is the grid optimization stage. According to the effective monitoring range of a single monitoring station in the area obtained in the second stage, the optimal grid density and aspect ratio are obtained by using the optimization analysis technology, so as to achieve full coverage of the monitoring area with the least number of monitoring points. See Figure 4, which are the original uniform grid scheme, the summer grid layout scheme and the winter grid layout scheme. By calculating the optimal grid aspect ratio in summer is 1:2.3, and the optimal grid aspect ratio in winter is 1 :3.

Referring to FIG. 5 , it is a schematic diagram of an original uniform grid coverage effect provided by an embodiment of the present invention without grid adaptation and optimization. Under the uniform grid, the grid coverage is 39% in summer and 22% in winter. It can be seen that the uniform grid detection effect before optimization is not ideal.

This method is suitable for the following specific situations:

(1) When discussing the monitoring of pollutants in urban space, the dominant wind speed and wind direction during the study period provided by the meteorological station are mainly considered to simulate and calculate the flow field in urban space. Therefore, this study is based on the steady flow field. superior.

(2) The pollutant source is a point source with a constant release intensity. The probability-based adjoint method can only reversely identify the point source type (or can be considered as a point source) pollutant source, and the line source and area source are not within the scope of this study.

(3) The pollutants are inert pollutants, and the airflow followability is good. For convenience, this study only focuses on inert pollutants with better airflow following. And if you want to further consider the particulate pollutants that can react with other substances in the atmosphere or have poor airflow following, as long as the simulation calculation is accurate, this method is also applicable.

Claims (2)

1. a grid arrangement method of air pollutant monitoring site, is characterized in that, comprises the following steps: The first step: lay out the coarse grid; For monitoring large areas, firstly, a uniform grid with an aspect ratio of 1:1 is used. Then, according to the investigation of the local population and industry distribution, the frequency of pollution, and the historical data of the pollution impact range, the densely populated and industrial enterprises are clustered. . Refine grids in hotspot areas with frequent historical pollution phenomena, and determine the grid refinement ratio through grid independence test; The second step: improve the fitness of the grid in the hotspot area; Obtain the local wind speed and wind direction parameters as the velocity inlet boundary conditions, use computational fluid dynamics to solve the Navier Stokes equation, and calculate the flow field in the study area; the coordinates of a hot spot and the monitoring concentration threshold (P ,C) Substitute into the adjoint equation of the pollutant propagation equation:

where Ψ ^* is the accompanying probability factor for the location,

is the detection area position vector,

is the position vector of the measuring point, C represents the pollutant concentration, u _j is the velocity in the direction of the x _j axis, ν _{c, j} represents the turbulent diffusion coefficient of the pollutant in the x _j direction, and q ₀ is the unit volume of the negative source of pollutants Flow, Γ ₁ , Γ ₂ and Γ ₃ are boundary conditions, _{ni is the unit vector in the direction of the x i axis} ;

is the load term, and its expression is as follows:

Solving the equation yields an adjoint probability distribution for the location of potential pollution sources

Substitute it into and solve the following probability equation (1-3), and obtain the accompanying probability distribution of the potential pollution source locations corresponding to the release intensity of different pollution sources. That is, the monitoring range of the monitoring station under the condition of the source strength:

in

and

are the position P corresponding to the monitoring station and the monitoring concentration threshold, respectively, M is the emission intensity of the pollution source,

is the probability distribution of the corresponding pollution source release intensity M and location x obtained according to the monitoring concentration threshold;

The distribution is in the form of a normal distribution:

where σ _ε is the measurement error of the instrument; The third step: for the grid optimization stage; According to the effective monitoring range of a single monitoring station in the site obtained in the second stage, the optimal grid point density and aspect ratio are obtained by using the optimization analysis technology, and the minimum number of monitoring points is used to achieve full coverage of the monitoring area. 2 . The grid arrangement method of an air pollutant monitoring site according to claim 1 , wherein the σ _ε is set to 20% for the measurement error of the instrument. 3 .

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